I have a large number of them that I picked up at yard sales. You may wish to consider doing that. Mine are in very good shape, are very sturdy, attractive and are in a wide range of sizes. You can still purchase the rubber rings in grocery stores. I prefer the rings. The disks are easier to work with but they can rust (and should be replaced after 1 use).

I just found a source of these (just very small ones, however) - the Wildly Delicious Foods warehouse sale on Railside Road in Toronto. You can buy them filled with a sea salt mix for $3, or empty for $2. I was thrilled to see these and wanted to share!